A thankful heart is not only the greatest virtue, but the parent of all the other virtues. [Lat., Gratus animus est una virtus non solum maxima, sed etiam mater virtutum onmium reliquarum.]
"Oratio Pro Cnæo Plancio", XXXIII, as quoted in Hoyt's New Cyclopedia Of Practical Quotations (1922), p. 336-37,